Advantech PCIE-1802, User Manual

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PCIE-1802 User Manual 16
3.3.1 I/O Connector Signal Description
3.3.2 Analog Input Connections
3.3.2.1 Differential Inputs
The PCIE-1802 supports two terminal configurations for analog input: differential and
pseudo-differential. The term pseudo-differential refers to the 50
Ω resistance
between the outer connector shell and chassis ground.
If the signal source is floating, use the pseudo-differential configuration. The pseudo-
differential configuration provides a ground reference between the floating source
and the PCIE-1802 by connecting a 50
Ω resistor from the negative input to ground.
Without this, the floating source can drift outside of the input common-mode range of
the PCIE-1802.
If the signal source is grounded or ground referenced, both the pseudo-differential
and differential input configurations are acceptable. However, the differential input
configuration is preferred, since using the pseudo-differential input configuration on a
grounded signal source creates more than one ground-reference point. This condi-
tion may allow ground loop current, which can introduce errors or noise into the mea-
surement. The 50
Ω resistor between the negative input and ground is usually
sufficient to reduce these errors to negligible levels, but results can vary depending
on your system setup.
Configure the channels based on the signal source reference or DUT configuration.
Refer to Table 1-1 to determine how to configure the channel.
The default configuration of the PCIE-1802 is differential.
Signal Name Reference Direction Description
AI<0..7>+ AGND Input Analog positive input channels 0 through 7
AI<0..7>- AGND Input Analog negative input channels 0 through 7
AGND ---- ---- Analog ground
REF_CLK_IN DGND Input 25 MHz reference clock input
REF_CLK_OUT DGND Output 25 MHz reference clock output
DTRG<0..1> DGND Input Digital trigger inputs
TRIGOUT<0..1> DGND Output Trigger outputs
SYNC_IN DGND Input Synchronization input
SYNC_OUT DGND Output Synchronization output
DI0 DGND Input Digital input channel
DO<0..1> DGND Output Digital output channels
DGND ---- ---- Digital ground
Table 3.2: Recommended Analog input Channel Configuration
Source Reference Channel Configuration
Floating Pseudo-differential
Grounded Differential